Automatic headlight dimmer



Ogt. 19, 1948. R. A. EDELL 2,451,543

AUTOMATIC HEADLIGHT DIMMER Filed April 1, 1946 INVENTOR.

' R/CHARD A. 5051.

BY :51: E; E I 6% '1';- lorwey Patentecl Oct. 19, 1948 UNITED STATES PATENT OFFICE Claims.

This invention relates to improvements in control mechanisms for the electrical headlight lighting systems of vehicles, such as automoblles, and more especially to such control mechanisms which are responsive to the light rays of the headlights of on-coming vehicles for automatically switching from the bright-lighting to the dim-lighting circuits.

An important object of my invention is to provide a control mechanism of the above character which is so constructed and arranged as to maintain the lighting circuit which is in operation closed against vibrations and shocks incident to travel of the vehicle over the road. More particularly the control mechanism contemplates the provision of a relay comprising a permanent magnet for normally holding an armature in circuit-closing position, said magnet being connected in electrical circuit with a light sensitive cell which picks up the rays of the light of oncoming vehicles. The cell creates a flux in its circuit in counter-polar relation to the magnet, thus overcoming the field of the magnet, and causes the armature to be attracted away from the magnet breaking the bright-lighting circuit and closing the dim-lighting circuit to the headlights.

Another object of my invention is to provide a control mechanism of the above character which includes a light-sensitive cell for actuating a detector circuit and a lens for collecting and focusing the rays from the lights of oncoming vehicles onto the cell, the lens being so constructed and arranged as to screen from the cell light rays of only nominal intensity but to pass the rays of higher intensity such as are ordinarily emitted by the headlights of automobiles in the road.

Still another object of my invention is to provide a control mechanism of the above character which is entirely electrical in operation and which does not require the use of springs, weights or other mechanical means-the action of which is unreliable because of sidesway, vibrations and shocks imparted to the vehicle during its travel over the road-for maintaining the headlight lighting circuits closed.

Other objects and advantages will be apparent from the following detailed description of a preferred embodiment of the invention, reference being had to the annexed drawing in which:

Figure 1 is a diagram of an electrical headlight lighting system for automobiles;

Figure 2 is a diagram of a modified form of the secondary circuit shown in Fig. 1; and

Figure 3 is a detail view of the permanent magnet included in the circuits of Figs. 1 and 2.

In Fig. l is shown a wiring diagram of an automatic dimming system for the headlights of automobides, comprising a detector Circuit I, a lighting circuit 2, and a relay 3 for controlling the lighting circuit.

The detector circuit comprises a conductor Ia grounded at its opposite ends to the frame of the automobile and includes a light sensitive or selenium cell A; suitably located on the front end of the automobile. The cell is positioned at the rear of a housing 5 within which is contained a double convex lens 6, an amber-colored glass screen I and a window piece 8, the arrangement being such that the light rays emitted by the headlights of the on-coming vehicles are collected and focused by the lens onto the cell. The function of the glass screen is to allow only the passage of light rays of a brilliance such as are ordinarily projected by the headlights of vehicles under road driving conditions at night.

Included in the detector circuit is a coil 9 having a soft iron core l0 which is energized by the flow of current through this circuit. Also included in the detector circuit are two coils H and Ila encircling the legs l2 and l2a respectively of a permanent U-shaped magnet H3. The magnet I 3 is strongly magnetized and the two coils H and Ila encircling the legs l2 and |2a of the magnet are so wound as to create a flux in opposition to the polarity of the magnets when a current is flowing through the detector circuit.

The lighting circuit includes the two headlights l4 each containing a double filament l5, namely a bright lighting filament i5a and a dim lighting filament [5b. The bright lighting filaments We of the headlights are connected in parallel to a conductor i6 extending to a contact I! and the dim lighting filaments 151) are similarly connected to a conductor 58 leading to a contact IS, the opposite side of the filament circuits being connected to ground through a conductor 20.

An armature 2| pivoted at one end and made of magnetizable material is normally held by the permanent magnet I 3 so as to engage the contact I1, but upon energization of the detector circuit it is adapted to be attracted by the electromagnet ill so as to swing to the dotted line position engaging the contact 19. A conductor 22 extending from the armature 2| includes a source of electrical energy 23, which may be the usual battery or generator which supplies ignition current for the engine, and the end of this conductor is grounded to the frame of the automobile. The conductor la of the detector circuit ties into the conductor 22 at point 24' forming a shunt with respect to the load-carrying conductor 22. A hand-operated switch 25 in line 22 located, for example on the instrument panel or at any other convenient location upon the automobile, permits turning the headlight circuit on and off.

The operation of the circuit controlling mechanism just described is as follows: At such times as no current is flowing in the detector circuit I, the attraction of the permanent magnet holds armature 2| in secure engagement with contact l1 eliminating all possibility of breaking the cir- I cuit due to vibrations on rough roads and allowing current to flow from the battery or generator 23 through conductor 22, armature 2i, conductor l6 and the bright filaments 15a of the headlights I4.

' Upon approach of another vehicle on the road the light rays of the approaching 'vehicle are converged by means of the double convex lens through the amber glass screens 1 and, concentrated on the light-sensitive point of the cell 4. Amber-glass screen i is resistant to the rays of all ordinary lights and to the lights of the approaching vehicle until such rays reach a blinding intensity at approximately 500 feet distance. At this point of intensity, the cell energizes the detector circuit 2, pas'singcurrent through the coils of the electromagnet 9 and through the coils ll and Ila encircling the poles of the permanent magnet.

When current of sufficient magnitude flows through the detector circuit, an adverse flux is set up in coils II and Ila sufficient to overcome or neutralize the attraction of the permanent magnet, thus releasing the armature 2| to the attraction of the electromagnet 9 which is simultaneously energized by the current flowing in the detector circuit. Armature 2| then swings into the dotted line position breaking engagement with contact H and making engagement with contact l9. Current now flows from battery or generator 23, through conductor zz'armature 2| and conductor 18 to the dim lighting filaments le'b.

After the on-coming vehicle has passed and the light-sensitive cell A is no longer within range of its headlights, the detector'circuit'is once again die-energized, the fluxes in the coils 9, i l and I la collapse, and-the armature drops back, under the influen-ce'of permanent magnet IE, to the position shown in full lines thus re-establishing the'=bright-lightingcircuit to the headlights.

A modification of this circuit controlling mechanism is illustrated in Fig. 2. In this figure the detector circuit, not shown, is substantially the same as was described in connection with the first-described mechanism, the difierence residing wholly 'in the headlight lighting circuit. The headlights according to this modification are of the single filament type, each headlight having a filament 33, one of thesidcs of which is connected to ground through alconducto'r 31 and the other of thesides being connected in parallel to a conductor 32, having branched ends 32a and 32b terminating respectivel at the contacts 5? and 19. The branch 32b is provided with a resistor 33.

Byvirtueof this construction, the armature?! is normally'held by the permanent magnet l3 of the relay: 3in engagementwitht'he contact l1,'all'owing current to flow through branch 32a and conductor 32 to cause the bright lighting of the headlight filaments. When, however, the armature is attracted by the electromagnet 9, due to energization of the detector circuit, it breaks connection with contact l1 and moves into the position indicated in dotted lines to engage the contact l9. Current then flows through the branch 32b, resistance 33 and conductor 32 to dim the filaments, the extent of the dimming being determined by the amount of resistance 33 in the circuit.

The permanent magnet 13 constitutes a part of the relay 3 of both of the control mechanisms described above is more clearly shown in Fig. 3. This magnet comprises the two legs, or poles, l2 and 12a, connected at one end by a bridge I21). The coils II and Ila are wound on spools l2c surrounding the legs of the magnet and the turns of the coils are in a direction such that the current flowing in the detector circuit creates a flux in oppositionand approximately equal in value to the strength of the poles of the magnet, thus neutralizing the pull exerted by the magnet on the armature M. The parts 12, 12a and I2!) are composed of suitable magnetic metal strongly magnetized and possessing a high degree of retentivity capable of resisting permanent loss of magnetism or reverse magnetization under influence of the coils H and Na.

While a preferred specific embodiment of the invention has been set forth, it is to be understood that the invention is not limited to the exact constructions illustrated and described, but much fications of these details may be made Within the purview of the appended claims.

I claim:

1. An automatic light dimming mechanism for vehicles comprising a detector circuit including a light-sensitive cell, a dim-lighting circuit and a bright-lighting circuit, a movable armature actuable for alternately opening and closing said dim-lighting and bright-lighting circuits, a relay for'actuating said armature, said relay compris ing a permanent magnet adapted to normally attract and hold said armature in closing position with respect to the bright-lighting circuit and a coil connected in the detector circuit'and winding about sai'd magnet in-a direction such as to create a magnetic fiux in'opposition to and of approximately the same magnitude as the polarity of the magnet, and an electromagnet in the detector circuit adapted to attract saidarmature to break the bright-lighting circuit and close the dim-lighting circuit upon energization of the detector circuit.

2. An automatic light-dimming mechanism for vehicles comprising a detector circuit including a light-sensitive cell, a dim-lighting circuit and a bright-lighting circuit,-a movable armature act able for alternately opening and closing said dim lighting and, bright-lighting circuits, a relay for actuating said armature, said relay comprising a double legged U -'sh'ape'd permanent magnet adapted'to normally attract and hold said armature in closing position with respect 'to' the bright lighting circuit and" coils connected in the detector circuit and winding about the legs of'said magnet in a direction such. as to create a magnetic flux in opposition to the-polarity 'oi the magnet, and an electromagnetin the detector circuit adapted to attract, said armature to break the brightlighting circuit, andclosev the dim-lighting circuit upon energization of the detector circuit.

3. An automatic light-d-imming mechanism as set forth in claim 1 in which the bright-lighting 5 6 and dim-lighting circuits include bright and dim bright-lighting circuit and close the dim-lighting filaments of a double filament lamp. circuit upon energization of the detector circuit. 4. An automatic light-dimming mechanism as RICHARD A. EDELL. set forth in claim 1 in which the dim-lighting circuit includes a resistor. 5 REFERENCES CITED In an automatic light dlmmmg mechamsm The following references are of record in the for vehicles of the class comprising a detector fil of this patent; circuit including a light-sensitive cell, a dimlighting circuit and a bright-lighting circuit and UNITED STATES PATENTS a movable armature actuable for alternately open- 10 N b N m Dat ing and closing said dim-lighting and bright 685,431 Pearson Oct. 29, 1901 lighting circuits, the combination with said arma- 1,106,372 Eisenmann Aug. 11, 1914 ture of a relay for actuating the armature, a per- 2,056,745 Stalnaker Oct. 6, 1936 manent magnet adapted to normally attract and 2,086,865 Gustafson Jul 3 937 hold said armature in closing position with respect 1 2,188,803 Boehne Jan. 30, 1940 to the bright-lighting circuit and a coil connected 2,375,677 Moore May 8, 1945 in the detector circuit and winding about said magnet in a direction such as to create a mag- FOREIGN PATENTS netic flux in opposition to and of approximately Number Country Date the same magnitude as the polarity of the magnet, 245,084 Great Britain Dec. 3, 1925 and an electromagnet in the detector circuit ,768 ea B a ay 2, 1940 adapted to attract said armature to break the 

